Hybrid NHC ligands and complexes in which an oxygen-donor type functionality is associated with the carbene donor are surveyed.

The new alcohol- and ether-functionalised-NHC silver(I) complexes bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C₂OH)}₂]Cl (4), bis(1-(2-hydroxyethyl)-3-mesityl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMes(C₂OH)}₂]Cl (5), bis(1-(2-hydroxyethyl)-3-methyl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMe(C₂OH)}₂]Cl (6), bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) tetrafluoroborate, [Ag{ImDiPP(C₂OH)}₂]BF₄ (9), and bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C₂OMe)}₂]Cl (13), were synthesized and fully characterized by NMR spectroscopy and single crystal X-ray diffraction. For some complexes, an uncommon heteronuclear coupling ⁴J(^107/109Ag–H) was unveiled. Their ability to transfer the NHC ligand to Ni(II) was assessed in the presence of different nickel(II) sources; the bis-NHC Ni(II) complex bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)nickel(II) chloride, [NiCl₂{ImDiPP(C₂OMe)}₂] (15), was obtained from 13 and shown by X-ray diffraction study to have a trans-arrangement of the two NHC ligands. However, in contrast to other Ag(I) NHC complexes the transmetallation reaction failed with the hydroxyl-functionalised silver complexes, possibly due to the acidity of the alcohol OH function, leading overall to reprotonation of the C_NHC and isolation of the corresponding imidazolium salts.

To develop greener protocols toward the sustainable production of conjugated polymers, we combine the advantages of atom-economic direct arylation polycondensation (DAP) with those of the green solvent 2-methyltetrahydrofuran (MeTHF). The n-type copolymer PNDIT2 is synthesized from unsubstituted bithiophene (T2) and 2,6-dibromonapthalene diimide (NDIBr₂) under simple DAP conditions in MeTHF. Extensive optimization is required to suppress nucleophilic substitution of NDIBr end groups, which severely limits molar mass. Different carboxylic acids, bases, palladium precursors and ligands are successfully screened to enable quantitative yield and satisfyingly high molar masses up to M_n,SEC ∼ 20 kDa. In contrast to PNDIT2 made via DAP in toluene with tolyl-chain termini, nucleophilic substitution of NDIBr chain ends in MeTHF finally leads to NDI-OH termination. The influence of different chain termini on the optical, thermal, structural and electronic properties of PNDIT2 is investigated. For samples with identical molecular weight, OH-termination leads to slightly reduced aggregation in solution and bulk crystallinity, a decreased degree of alignment in directionally deposited films, and a consequently reduced, but not compromised, electron mobility with promising values still close to 0.9 cm² V⁻¹ s⁻¹.

The reactions of NiCl₂·2H₂O or [NiCl₂(DME)] (DME = dimethoxyethane) with 2-methyl-1-(pyridin-2-yl)propan-2-ol (HL) and 2-(pyridin-2-yl)ethanol (HL_Et), in a 1 : 1 ratio, afforded the tetranuclear, cubane-type clusters [Ni(μ₃-Cl)Cl(HL)]₄ (3) and [Ni(μ₃-Cl)Cl(HL_Et)]₄ (4), respectively. These are tetramers of the hypothetical mononuclear formula-isomers [NiCl₂(HL)] and [NiCl₂(HL_Et)], respectively, and represent rare examples of structurally characterized cubane-like transition metal dihalogenide complexes. The 2 : 1 reactions between HL or HL_Et and [NiCl₂(DME)] yielded, instead, the mononuclear [NiCl₂(HL)₂] (1) and the dinuclear complex [Ni(μ-Cl)(HL_Et)₂]₂Cl₂ (2), respectively. The reaction of 3 with NaOH afforded selectively the cubane-type cluster [Ni(μ₃-OH)Cl(HL)]₄ (5) which differs only in the nature of the capping anions (Cl vs. OH, respectively). The magnetic properties of the unusual tetranuclear cubanes 3 and 5 have been investigated and revealed in both cases single-molecule magnet (SMM) behaviour.